This invention relates to the discovery and asexual propagation of a new variety of grapevine as herein described and illustrated. The new variety was first hybridized by David. W. Cain and Michael J. Striem in Wasco, Kern County, Calif., the variety being originated by controlled hybridization and subsequent culture of seed traces and embryo rescue procedures.
The new variety ‘Sugrathirtyone’ is characterized by possessing medium sized green-yellowish seedless grapes having a mild neutral flavor. The grapes have an elliptic shape, a crisp flesh texture, medium sugar content and excellent eating quality. The new variety ‘Sugrathirtyone’ is exceptional with its late ripening, as the grapes ripen after any other seedless grape cultivars grown and marketed commercially in California. Further, the bunches are able to stay on the vine for a month or more, while still maintaining commercial harvest quality.
The new variety ‘Sugrathirtyone’ was created by hybridization of two “seedless” grapes possessing small, abortive, vestigial ovules. From the initial population of hybrid ovules, embryo rescue methods were used to produce a population from which the present variety was selected. The seed parent is ‘92147-050-238’ (unpatented) and the pollen parent is ‘92187-055-030’ (unpatented). The parent varieties were first crossed in May 1999, with the date of first sowing being August 1999, and the date first flowering being May 2001.
The new ‘Sugrathirtyone’ variety was first asexually propagated by Dr. Michael Striem in December 2001 in Wasco, Kern County, Calif. using hardwood cuttings.
The new variety ‘Sugrathirtyone’ resembles its seed parent ‘92147-050-238’ in berry color and shape. However, ‘Sugrathirtyone’ has a much larger natural berry size of approximately 4.55 grams, compared to the seed parent's natural berry size of approximately 3.35 grams. Additionally, the seed parent has a noticeable, dark and hard seed-trace while the seed-trace of ‘Sugrathirtyone’ is very small and soft.
The new variety ‘Sugrathirtyone’ resembles its pollen parent ‘92187-055-030’ in berry color and shape. However, ‘Sugrathirtyone’ has a much larger natural berry size of 4.55 grams, compared to the pollen parent's natural berry size of 4.26 grams. Further, while the berries of the pollen parent turn brown when exposed to direct sunshine, the berries of the new variety ‘Sugrathirtyone’ stay light-green with a milky-creamy/opaque look, turning slightly yellowish at the end of the harvest season.
The new variety ‘Sugrathirtyone’ is similar to the comparable variety ‘Sugraone’ (U.S. Pat. No. 3,106) in its appearance, bunch structure and berry shape. However, the new variety ripens about 6-8 weeks later than ‘Sugraone.’ The new variety ‘Sugrathirtyone’ also develops higher sugar levels than ‘Sugraone’ at harvest.
It is to be understood that variations of the usual magnitude from the described above may occur with changes in growing conditions, irrigation, fertilization, pruning, management and climatic variations.
The new ‘Sugrathirtyone’ variety has been shown to maintain its distinguishing characteristics through successive asexual propagations by, for example, cuttings.